Genome sequencing of Streptomyces aureofaciens DM-1 and analysis of 6-demethylchlortetracycline biosynthesis gene cluster / 生物工程学报

Streptomyces aureofaciens DM-1 is a high-yielding 6-demethylchlortetracycline producer. The genome sequencing of DM-1 reveals a linear chromosome containing 6 824 334 bps nucleotides with GC content of 72.6%. In this genome, a total of 6 431 open reading frames were predicted by using glimmer 3.02, Genemark and Z-Curve softwares. Twenty-eight secondary metabolite biosynthetic gene clusters were uncovered by using AntiSMASH gene prediction software, including the complete 6-demethylchlortetracycline biosynthetic gene cluster. A frame-shift mutation in methyltransferase coding region was detected, which may result in the demethylation of chlortetracycline. The complete genome sequence of S. aureofaciens DM-1 provides basic information for functional genomics studies and selection of high-yielding strains for 6-demethylchlortetracycline.

Study on experimental model of transplacental infection of coxsackievirus B_3 from the mother to the fetus in late gestation mice / 中国临床药理学与治疗学

AIM: To study the possibility and conditions of transplacental infection of coxsackievirus B3(CVB 3) from pregnant mice to their fetuses and newborns. METHODS: Coxsackievirus B 3 strain causing balb/c mice myocardial injury(CVB 3m )was inoculated with 10 5 TCID 50 in dose into the mother mice at 6-7 days (early gestation),9-10 days (middle gestation) and 17-18 days (late gestation) of gestation, in contrast with non pregnant mice. Some placentas and fetuses were removed by caesarean section before mothers partusing; some mothers and their babies were sacrificed after parturition, and virus isolation, serological and pathological tests were performed. RESULTS: Viramiae was observed in mother mice of late gestation inoculated with CVB 3m at a fit amount on the second day after inoculation, while no newtralizing antibody to CVB 3m was detected in blood. The virus was isolated from cardiac muscles of inoculated mother mice in different gestation and the controls. The virus was also isolated from some placentas and fetuses, and both sera and cardiac muscles of infants in the late gestation (virus titer were all 10 -2 -10 -3 ). On d 7 of inoculating virus, pregnant and non pregnant mice titers of neutralizing antibody to CVB 3m in sera were all between 1160 and 1320. Under the electromicroscopy, some cardiac muscle cells of mother or infant mice appeared with morphological changes and little hollow bubbles occured in cytoplasm. The fibers broke off, and the bright and dark belts became indistinct. CONCLUSION: The amimal model, intraplacental passage of CVB 3 from pregnant mother in late gestation to fetus in mice, is a benefitial tool to study enterovirus diseases in human perinatal period.